HarmonyOS 鸿蒙Next：base64格式的图片怎么保存到相册

saveImage() {
    //文件保存路径
    let uri = '';
    try {
      let PhotoSaveOptions = new picker.PhotoSaveOptions();
      //保存图片默认名称
      PhotoSaveOptions.newFileNames = ['test.png'];
      let photoPicker = new picker.PhotoViewPicker();
      //调起系统的图片保存功能
      photoPicker.save(PhotoSaveOptions).then((PhotoSaveResult) => {
        uri = PhotoSaveResult[0];
        //获取图片的base64字符串
        let imageStr = '图片的base64字符串'.split(',')[1];
        //打开文件
        let file = fs.openSync(uri, fs.OpenMode.READ_WRITE);
        //base64字符串转成buffer
        const decodeBuffer = buffer.from(imageStr, 'base64').buffer;
        //写入文件
        fs.writeSync(file.fd, decodeBuffer);
        //关闭文件
        fs.closeSync(file);
      }).catch((err: Error) => {
        console.error(err + '');
      })
    } catch (e) {
      console.error(e);
    }
  }<button style="position: absolute; padding: 4px 8px 0px; cursor: pointer; top: 8px; right: 8px; font-size: 14px;">复制</button>